Preparation And Photocatalytic Activity Of Bismuth Molybdate Nanomaterials

Semiconductor photocatalysis and photocatalytic materials are the effective means to solve energy shortage and environmental pollution.Among various photocatalytic materials,bismuth molybdate has a simple Olive Chis（Aurivillius）layered structure with good visible light response.It shows excellent performance for environmental pollution treatment,solar photolysis hydrogen production,gas sensing and so on.However,there are still many technical bottlenecks before the practical application of bismuth molybdate photocatalyst,such as the optimization of the synthesis process,the design and preparation of new catalyst structure,and further improvement of visible light photocatalytic performance.This paper will focus on the optimization of photocatalytic performance,The effect of surfactants on the bismuth molybdate morphology and catalytic properties was studied by the hydrothermal and solvothermal methods.Silver nanoparticles and Bi2S3 composites with Bi₂MoO₆ were synthesized to further enhance the photocatalytic properties of bismuth molybdate.The main research contents and conclusions are as followed:In order to analyze the effect of surfactants on the synthesis,structure and properties of bismuth molybdate,Bi₂MoO₆ nanosheets were prepared by hydrothermal method with different surfactants.The effects of surfactant types（CTAB,KBr,PVP,PEG）on the structure of Bi₂MoO₆ were studied,and the growth mechanism of CTAB was also discussed.When CTAB=0.15 g,the thickness of the synthesized nanosheets was only 5～15 nm,and the specific surface area was 20.551 m2/g.Compared with the bismuth molybdate nano powder,bismuth molybdate nanosheet prepared with CTAB as surfactant has stronger light absorption,lower band gap and better photocatalytic activity.After 3 h after irradiation,methylene blue（MB）degradation rate achieves 81%.Using CTAB as surfactant,flower like Bi₂MoO₆ microspheres were produced in ethylene glycol/water mixed solvent by thermal method.The Bi₂MoO₆ micspheres are by assembly of nanosheets with thickness of 10～20 nm self assembled,and the morphology and size of Bi₂MoO₆ microspheres could be controlled by changing the mixed solvent ratio.The growth mechanism of flower like microspheres was analyzed.Hollow lower like Bi₂MoO₆ structure synthesized at EG/H2O of 8:2 has better photocatalytic activity than flakes and flower like microspheres.After 3 h irradiation,the degradation rate of MB can reach 98%.Based on the above mixed solvothermal method,Ag loaded Ag/Bi₂MoO₆ was synthesized by one-step solvothermal method and photoreduction method,respectively.The results showed that hollow spherical Ag/Bi₂MoO₆（Ag=6wt%）formed by one-step solvent thermal method has narrow band width and thus has a better visible light absorption effect.On this basis,we also discussed the growth mechanism of hollow ball.The Ag/Bi₂MoO₆ sample prepared by one-step solvothermal method was used as photocatalyst,and the degradation rate of MB reached 90.2%after 3 h visible light irradiation.Based on the solvothermal method,the Bi2S3/Bi₂MoO₆ composite structure with nanorod/microsphere morphology was prepared by one-step solvothermal method.In this structure,the photogenerated electrons can be transferred on the interface between Bi2S3 and Bi₂MoO₆,so that the photogenerated electron hole pairs can be separated effectively,and the carrier mobility can be increased.The photocatalytic performance of the prepared Bi2S3/Bi₂MoO₆ composite structure was better than that of Bi₂MoO₆ micro spheres prepared under the same conditions,and the degradation rate of MB reached 83%after 3 h visible light irradiation.